Recirculating gas blast interrupter



Nov. 3, 1959 J. D. WOOD RECIRCULATING GAS BLAST INTERRUPTER 3 Sheets-Sheet 1' Filed June 21, 1957 INVENTOR awe/w 0. W400 Ar/zwx Nov. 3, 1959 J. D. WOOD RECIRCULATING GAS BLAST INTERRUPTER 3 Sheets-Sheet 2 Filed June 21, 1957 INVENTOR. diff/ y 0. W400 AT/a YM Nov. 3, 1959 .1. D. WOOD RECIRCULATING GAS smsr INTERRUPTER 3 Sheets-Sheet 3 Filed June 21, 1957 United States Patent 2,911,507 RECIRCULATING GAS BLAST INTERRUPTER Joseph D. Wood, Wayne, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application June 21, 1957, Serial No. 667,201 5 Claims. (Cl. 200-448) This invention relates to circuit interrupters of the gas blast type and more particularly to a circuit interrupter having a recirculating gas system wherein the cooperating contacts are always surrounded by high pressure gas.

When a circuit interrupter protecting a current carrying line is opened, an electric current are is drawn between the parted contacts. At this time rapid interruption of the arc and the prevention of restrike once interruption has taken place are of prime consideration.

A gas blast directed at the arc hastens the deionization thereof by cooling the arc and exhausting the hot arcing products from the region between the parted cooperating contacts. All other factors being equal, the larger the gap between the parted contacts the lesser the likelihood of arcrestrike. But a larger gap necessarily means a greater overall size for the interrupter. However, by raising the pressure of the gas in the gap, the separation distance between the parted contacts may be reduced without danger of restrike at a given voltage. That is, the ability of a dielectric gas to resist breakdown at a given voltage gradient increases as the gas pressure increases except at pressures considerably below atmospheric pressure.

It has been found that the so called electronegative gases, such as sulphur hexafluoride (SP6) and sulphur monofiuoride (SZFZ), are superior to air in their deionizing and dielectric properties thereby making them particularly useful in arc interruption. When gases other than air are used, a recirculating gas system should be employed because of the high cost of these gases.-

Further, a recirculating system prevents the external introduction of contaminants into the gas and includes filters to remove arcing products thereby assuring a continuous supply of gas in which the dielectric strength, cooling properties, and interrupting ability is at a maximum.

Gas blast interrupters of the prior art usually stored high pressure gas in a tank forming part of the interrupter structure. At the instant of contact separation, or immediately prior thereto, a valve operatively connected to the contacts was opened to introduce the high pressure gas in the gap between the parted contacts. The introduction of high pressure gas was accompanied by turbulence which decreased the gas flow rate along the arc stream thereby preventing a rapid arc extinction. In interrupters employing a bridging member moving transversely with respect to the stationary contacts, the initial gas blast was required to transfer the are from the bridging contact to a stationary contact rather than cool the are thereby further delaying arc extinction.

Part of the blast gas was diverted to open an isolating switch when interruption was complete. The contacts were reclosed by springs as the blast pressure dropped. Closing the isolating switch once again completed the circuit.

The circuit interrupter of the instant invention includes a separate interrupter unit for each current carrying line of the electrical system being protected. Each 2,911,501 Patented Nov. 3, 1959 ably disposed therein. Movable contacts are carried by from the stationary contacts.

each of the pistons and are biased out of each end of the cylinder so that the movable contacts are in engagement with the stationary contacts when the interrupter is closed.

The interior of the interrupter tank is at all times directly connected to a high pressure reservoir or the output of a compressor so that the movable and stationary contacts are always immersed in high pressure gas. A chamber positioned in the center of the cylinder between the two pistons is at the same high pressure as the interior of the tank when the interrupter is closed.

To open the interrupter a blast valve is operated to interrupt the connection between the chamber and the tank and to connect the chamber to a low pressure reservoir. Since the pressure behind the pistons is now very low the high pressure gas in the tank acting on the front of the pistons is sufiicient to overcome the biasing forces, causing the pistons to converge and thereby separate the movable contacts from the stationary contacts, opening the circuit. 7

The movable contacts have central openings therethrough which, together with openings in the chamber, provide a continuous gas passage between the chamber and tank while the movable contacts are moving away In this manner the are drawn as the cooperating contacts are parted will immediately be acted upon by a smooth flowing blast of gas which rapidly deionizes and cools the arc and exhausts the are products to the low pressure reservoir. When the movable contacts have reached their most fully con verged position they will be forced against seats projecting from the chamber walls to thereby seal off the gas passage between the chamber and tank to prevent the pressure in the tank from dropping to too low a value. Since there is high pressure surrounding the parted contacts, the gap length between necessary to prevent restrike will be smaller than if the parted contacts were surrounded by gas at atmospheric pressure. The cooperating contacts are brought into engagement by connecting the chamber to the tank which equalizes the pressure on both sides of the pistons to permit the biasing means to urge the movable contacts to diverge and engage the stationary contacts.

Filters are provided between the low pressure reservoir and the compressor to remove the are products and thereby assure a supply of clean gas for subsequent interruptions.

Since high pressure gas always surrounds the engaged cooperating contacts, a smooth gas flow will act on the are from the moment of its inception. Smooth gas flow assures maximum interrupting and dielectric properties since the arcing products are rapidly carried away from the arcing gap and a fresh supply of clean gas is being continuously introduced into the gap until interruption is completed.

Accordingly, a primary object of the instant invention is to provide a circuit interrupter of the recirculating gas 3 gas blast from the moment of arc inception to achieve rapid arc interruption.

Still another objectis to provide a gas blast circuit interrupter wherein'gas pressure acting on the movable contact structure is employed to actuate the movable contacts in a converging movement from the engaged to the disengaged position to thereby permit a compact construction.

A further object is to provide a gas blast circuit interrupter wherein the contact carrying pistons serve as valve members to turn off the gas blast when the movable contacts have reached their fully disengaged positions and thereby maintain a'high pressure in the gap between the parted contacts.

A still further object is to provide a gas blast circuit interrupter wherein a movable contact structure in axial alignment with two stationary contacts is used to bridge the gap therebetween to effect circuit interruption.

These and other objects of this invention shall become more apparent after reading the following description of the accompanying drawings in which:

Figure 1 is a side elevation of a single interrupter unit, partially cut away to show the internal construction thereof, with the circuit closed.

Figure 2 is a section taken through line 2-2 of Figure 1 looking in the direction of arrows 2-2.

Figure 3 is a fragmentary view of the interrupter unit of Figure 1 with the circuit open.

Figure 4 is a schematic representation of a three conductor system protected by the circuit interrupter of the instant invention.

Figure 5 is a section taken through line 55 of Figure 1 looking in the direction of arrows 55.

Referring to the figures, interrupter unit comprises an elongated tank 11, which, together with its internal and external components, is symmetrical about the transverse center line of Figure 1. Only one half of the interrupter unit 10 will be described in detail, it being understood that the other half is merely a mirror image thereof.

Tank 11 comprises two cylindrical shells 12 joined at their first ends and having end plates 13 covering their second ends. Either or both shells 12 and end plates 13 may be constructed of insulating or conducting material as design considerations may dictate. Cover 14 fits over maintenance opening 15 in shell 12 with window 16 in cover 1 4 permitting a view of the interior of tank 11.

Stationary contact 17 is mounted to the end of stud 18 and is positioned within tank 11. Stud 18 passes through opening 19 in end plate 13 and is centered therein by insulator 20. Annular member 21 is secured to the end plate 13 outside of tank 11 to serve as a seal between insulator .and end plate 13. Corrugated bushing 32 lengthens creepagepath between stud 18 and the outside of tank 11.

Movable contact structure 25 is positioned in axial alignment with stationary contact 17 by means of insulator standolfs 26--29 which have their first ends abutting the outside of cylinder 30 and their second ends resting in outer ring 31 which is positioned between the end flanges 32 of shells 12 to provide a seal between the sections of tank 11 when they are joined as by bolts 33. A passage 34 extends through standoff 26, outer ring 31 and a fitting 35 secured to outer ring 31 for a purpose to be hereinafter fully explained.

Piston assembly 36, slidably mounted in cylinder 30 comprises a piston 37, a movable contact 38 secured to piston37, and a plurality of circularly arranged contacts 40 urged into wiping contact with the inside wall 39 of cylinder 30. Ring member 43 is force fitted to movable contact 38 to be in good electrical contact therewith while fastening means 58 secures plate ring 44 secured to ring member 43 to provide a guide for contacts 40 as they are biased radially outward from movable contact 38 by compression springs 41 which abut opposite ends of" adjacent contacts 40.

Closing springs 45 bear against piston 37 and bafile 46 positioned near the transverse center line of cylinder 36 to urge movable contact 38 out of cylinder 30 and into engagement with stationary contact 17 (Figure l) and thereby close interrupter unit 10. Baffle projection 47, piston opening'48, and piston depression 49 act as longitudinal guides for closing springs 45. Thus, a complete electrical path is formed between stud 18 on one side of interrupter unit 10 to stud 18 on the other side of interrupter unit 10 through stationary contact 17, movable contact 38, contact 40, cylinder 30 and the mirror image of these parts housed in the adjacent shell 12.

Bafiies 46 are spaced to form chamber 50, at the center of cylinder 36, which communicates with passage 34 through opening 51 in the wall of cylinder 30. Movable contact 38 is a hollow member having a central passage 54 extending through the complete piston assembly 36.. Baffle openings v55provide a gas passage from contact passage 52 to chamber 50 except when piston 37 is driven against seat 56 in the open position of interrupter unit 16) (Figure 3). Slots 53 may be cut in the face or mating surface of movable contact 38 and/or the face of stationary contact 17 to provide .a plurality of flexible fingers assure equal pressures .on both sides of piston assembly 36 when interrupter unit 10 is closed even though the opening or blast valve 60 may leak. The plurality of flexible fingers assures that contact between contacts 17 and 38 will be spread over a wide area rather than possibly being confined to a single point of contact.

With the interrupter unit 10 in the closed position of Figure 1, high pressure gas is present on both the front 58 and back 59 faces of piston assembly 36 so that closing springs 45 are free to urge the piston assemblies 36 in diverging directions into high pressure contact with stationary contact 17. To open interrupter unit10 blast valve 60 is opened by applying power to coil 61 which attracts plunger 62 to the left with respect to Figure 4 and thereby moves valve disc 64 oif seat 63, against the force of spring66. Chamber 50 now communicates with low pressure reservoir 65 through gas line 67, connected between fitting 35 and blast valve 60, and gas line v68, connected between blast valve 60 and low pressure reservoir 65.

Now the pressure on front face 58 is high and :the pressure on back face 59 is low so that piston assemblies 36 will be driven to a converging position where they will rest on seats 56 (Figure 3). As soon as an arc .is drawn between movable contact 38 and stationary contact 17 it will be subjected to a smooth flowing gas blast, flowing from tank 11 to low pressure reservoir 65, which cools and deionizes the are bringing about its rapid extinction. The arcing products are rapidly removed from the arcing gap by the gas blast and carried through the movable contact passage 54, chamber 50, passage 34, and gas lines 67, 68 to low pressure reservoir 65. If movable contacts 38 have pressure equalizing slots 53 cut therein the gas blast will be initiated at the moment blast valve 60 is opened. However, if movable contacts 38 do not have pressure equalising slots 53 the gas blast will begin at the moment the contacts 38, 17 part. Because of inertia and friction effects, the movement of'movable contact 38 will necessarily be delayed after opening blast valve 60.

By the time piston assembly 36 rests against seat 56 the arc is extinguished. The gas blast is shut off by seat 56 which seals off chamber 50 from contact passage 54. Packing 42 in peripheral groove 42' serves as a gas tight seal between piston 37 and the inside wall 39' of piston 30. High pressure gas is prcsent in the gap between cooperating contacts 38, 17, since tank 11 is connectedthrough fitting 70 and gas line 69 to high pressure reservoir 71, thereby preventing arc restrike.

When blast valve 60 is closed by deenergizing coil 61, i

interrupter unit will not close immediately since chamber 50 is not as yet filled with high pressure gas. Closing valve 72 must first be opened by energizing coil 73 which attracts plunger 74 and moves valve disc 75 upward 011? seat 76 against the force of biasing spring 77. At this time high pressure gas line 69 is connected to gas line 39 which in turn is operatively connected to piston chamber 50 thus bringing both sides 58, 59 of piston assembly 36 to the same pressure level and permitting closing springs 45 to expand and bring cooperating contacts 38, 17 into engagement.

Filter unit 83 is interposed between the input of compressor 84 and low pressure reservoir 65 to remove arcing products from the gas after it has interrupted a first arc and before it will be played on a second arc. The output of compressor 84 is connected to both high pressure storage reservoir 71 and high pressure gas line 69 to assure a continuous supply of high pressure gas within tank '11. Safety valves 82 are strategically placed through outthe system to bleed excess pressures back to the low pre'ssurereservoir 65 and prevent damage because of excessive gas pressures.

High pressure gas line 69 also has located therein check valves 85, a shut olf valve 89, reducing valve 88, and pressure switch 86. Reducing valve 88 controls the pressure level within tank 11 while pressure switch 86 controls the operation of compressor 84 responsive to the pressure in high pressure reservoir 71. Check valves 85 prevent a loss of pressure in tanks 11 even though the pressure in high pressure reservoir 71 or compressor 84 should drop below that of tank 11.

Control cabinet 90 houses pressure gauge 91 and operation counter 94 which is operated by means of auxiliary switch 93 and air valve 92 connected to gas line 39.

The three interrupter units 10 of Figure 4 may each be connected to a separate current carrying line to provide a double break in each line. However, for severe interrupting conditions two or more interrupter units 10 may be serially connected to produce four, six, eight, etc. breaks in a single power line.

Thus, an interrupter unit of the gas blast type has been provided which is of an especially compact and simplified construction achieved by:

(1) positioning the movable contact structures 25 between two spaced stationary contacts 17 in axial alignment therewith and providing axially movable contacts 38 which converge to open the circuit and diverge to close the circuit,

(2) having the pistons 37, which carry the movable contacts 38, acted upon directly by high pressure gas to effect circuit opening and also act as valves to stop the gas blast acting to interrupt the arc, when the cooperating contacts 38, 17 are fully separated,

(3) filling the gap between the cooperating contacts 38, 17 under open circuit conditions, with high pressure gas which is more effective insulator than gas at atmospheric pressure, and

(4) submerging the cooperating contacts 38, 17, under closed circuit conditions, in high pressure gas which is a more effective heat conductor than gas at atmospheric pressure. Furthermore, the presence of high pressure gas at the junction of the cooperating contacts 38, 17 assures a smooth flowing gas in the arcing gap at the moment the arc is first drawn.

The recirculating gas system also contributes in part tothe compact construction by supplying non-contaminated gas to the interrupter. Because of this, the safety factor used in calculating creepage distances within the tank 11 of the interrupter unit 10 may be kept to-a minimum since dirt and arcing products are not likely to build up on the insulating surfaces to impair their eifectiveness as insulators.

It should be apparent to those skilled in the art that a suitable construction of piston assemblies 36 will eliminate the necessity of forming chamber 50 by means of bafiles 46. Instead, the back faces 59 of the newly designed pistons will form chamber 50 and in the open position of the circuit interrupter, the newly designed piston assemblies will be positioned back to back and carry suitable formations which cooperated to act as a closed valve between passage 34 of insulator 26 and central passage 54 of movable contact 38.

In the foregoing, this invention has been described only in connection with preferred embodiments thereof. Many variations and modifications of the principles of this in vention within the scope of the descriptionherein are obvious. Accordingly, it is preferred to be bound not by the specific disclosure herein, but only by the appending claims.

I claim:

1. A gas blast type interrupter unit comprising a tank, a firstand a second stationary contact, a movable con tact structure; said first and second stationary contacts being disposed within said tank and axially aligned in spaced relationship with respect to each other; said movable contact structure being positioned between said'first and second stationary contacts in axial alignment therewith; said tank being operatively connected to a high pressure. source of dielectric gas; said movable contact structure comprising a cylinder and two piston assemblies slidably disposed therein; said piston assemblies being positioned in back to back relationship; resilient means urging said piston assemblies along diverging paths to a first position wherein the gap between said stationary contacts is bridged; means selectively connecting said movable contact structure to a low pressure source of dielectric gas and to said high pressure source; said piston assemblies being moved against the force of said resilient means along converging paths to a second position when said low pressure source is connected to said movable contact structure; said interrupter unit being open when said piston assemblies are in said second position with a double gap being formed between the ends of said movable contact structure and said stationary contacts; each of said piston assemblies comprising a piston and a movable contact having a first end secured to said piston; a second end of each of said pistons projecting beyond each end of said cylinders to engage said stationary contacts when-said piston assemblies are in said first position; passages extending from each of said first ends through said piston assemblies to the backs thereof; said passages communicating with said low pressure source when said piston assemblies are moving from said first to said second positions; said pistons acting as closed valves between said passages and said low pressure source when said piston assemblies are in said second position.

2. A gas blast type interrupter unit comprising a tank, a first and a second stationary contact, a movable contact structure; said first and second stationary contacts being disposed within said tank and axially aligned in spaced relationship with respect to each other; said movable contact structure being positioned between said first and second stationary contacts in axial alignment therewith; said tank being operatively connected to a high pressure source of dielectric gas; said movable contact structure comprising a cylinder and two piston assemblies slidably disposed therein; said piston assemblies being positioned in a back to back relationship; resilient means urging said piston assemblies along diverging paths to a first position wherein the gap between said stationary contacts is bridged; means selectively connecting said movable contact structure to a low pressure source of dielectric gas and to said high pressure source; said piston assemblies being moved against the force of said resilient means along converging paths to a second poopen when said piston assemblies are in said second pos'ition with a double gap being formed between the ends or said movable contact structure and said stationary contacts; each of said piston assemblies comprising a piston and a movable contact having a first end secured to said piston; a second end of each of said pistons projecting beyond each end of said cylinders to engage said stationary contacts when said piston assemblies are in said first position; passages extending from each of said first ends through said piston assemblies to the backs thereof; said passages communicating with said low pressure source when said piston assemblies are moving from said first to said second positions; said pistons acting as closed valves between said passages and said low pressure source when said piston assemblies are in said second position; a plurality of contacts for each of said movable'contacts; said contacts being operatively connected to said piston assemblies and movable therewith; said contacts being disposed between said movable contacts and the inside surface of said cylinder; means urging said contacts radially outward into engagement with said inside surface to secure a good electrical contact between said movable contacts and said cylinder.

3. A gas blast type interrupter unit comprising a tank, a first and a second stationary contact, a movable contact structure; said first and second stationary contacts being disposed within said tank and axially aligned in spaced relationship with respect to each other; said movable contact structure being positioned between said first and second stationary contacts in axial alignment therewith; said tank being operatively connected to a high pressure source of dielectric gas; said movable contact structure comprising a cylinder and two piston assemblies slidably disposed therein; said piston assemblies being positioned in back to back relationship; resilient means urging said piston assemblies along diverging paths to'a first position wherein the gap between said stationary contacts is bridged; means selectively connecting said movable contact structure to a low pressure source of dielectric gas to said high pressure source; said piston assemblies being moved against the force of said resilient means along converging paths to a second position when said low pressure source is connected tov said movable contact structure; said interrupter unit being open when said piston assemblies are in said second position with a double gap being formed between the ends of said movable contact structure and said stationary contacts; each of said piston assemblies comprising a piston and a movable contact having a first end secured to said piston; a second end of each of said pistons projecting beyond each end of said cylinders to engage said stationary contacts when said piston assemblies are in said first position; passages extending from each of said first ends through said piston assemblies to the backs thereof, said passages communicating with said low pressure source when said piston assemblies are moving from said first to said second positions; said pistons acting as closed valves between said passages and said low pressure source when said piston assemblies are in said second position; a plurality of slots at the junctions between said movable contacts and said stationary contacts; said slots providing communicating passages between said tank and said passages through said piston assemblies to assure gas flow at the instant said movable contact structure is operatively connected to said low pressure source.

4. .A gas blast type interrupter unit comprising a tank, a first-and a second stationary contact, a movable contact structure; said first and second stationary contacts being disposed within said tank and axially aligned in spaced relationship with respect to each other; said movable contact structure being positioned between said first and second stationary contacts in axial alignment therewith; said tank being operatively connected to a high pressure source of dielectric gas; said movable contact structure comprising a cylinder and two piston as- 8 semblies slidably disposed therein; said piston assemblies being in back to back relationship with a chamber therebetween; resilient means urging said piston assemblies along diverging paths to a first position wherein the gap between said stationary contacts is bridged; means selectively connecting said chamber to a low pressure source of dielectric gas and to said high pressure source; said piston assemblies being moved by high pressure gas in said tank acting on the fronts of said piston assemblies against the force of said resilient means along converging paths to a second position when said low pressure source is connected to said mo vable chamber; said'interrupter unit being open when said piston assemblies are in said second position with a double gap being formed between the ends of said movable contact structure and said stationary contacts; a passage extending through each of said piston assemblies from the front to the back; said passages communicating with said chamber when said piston assemblies are in said first position and when said piston assemblies are between said first and second positions; said piston assemblies acting as valves to in terrupt the communication between said passages and i said chamber when said piston assemblies are in said second position. V 5. A gas blast type interrupter unit comprising a tank,

a first and a second stationary contact, a movable coni tact structure; said first and second stationary contacts being disposed within said tank and axially aligned in spaced relationship with respect to each other; said movable contact structure being positioned between said first and second stationary contacts in axial alignment therewith; said tank being operatively connected to a high pressure source of dielectric gas; said movable contact structure comprising a cylinder and two piston assemblies slidably disposed therein; said piston assemblies being in back to back relationship with a chamber therebetween; resilient means urging said piston assemblies along diverging paths to a first position wherein the gap between said stationary contacts is bridged; means selectively connecting said chamber to a low pressure source of dielectric gas and to "said high pressure source; said piston assemblies being moved by high pressure gas in said tank acting on the fronts of said piston assemblies against the force of said resilient means along converging paths to a second position when said low pressure source is connected to said movable chamber; said interrupter unit being open when said piston assemblies are in said second position with a double gap being formed between the ends of said movable contact structure and said stationary contacts; a passage extending through each of said piston assemblies from the front to the back; said passages communicating with said chamber when said piston assemblies are in said first position and when said piston assemblies are between said first and second positions; said piston assemblies acting as valves to interrupt the communication between said passages and said chamber when said piston assemblies are in said second position; said low and said high pressure sources, said movable contact structure, and said tank comprising a closed path for a dielectric gas.

References Cited in the file of this patent UNITED STATES PATENTS 1,706,746 Rice Mar. 26, 1929 1,944,661 Kalwitz Ian. 23, 1934 2,125,525 Thommen Aug. 2, 1938 2,459,600 Strorn Jan. 18, 1949 2,470,628 Ludwig et al. May 17, 1949 2,757,261 Lingal et a1. July 31, 1956 2,805,305 Leopold Sept. '3, 1957 FOREIGN PATENTS 593,230 Great Britain Oct. 10, 1947 83 Germany Mar. 23, 1943 727,258 Great Britain Mar 30, 1955 

